Big transmasc passing tip
My personal biggest passing tip is dyeing your eyebrows with any brown box hair dye (adapt to your hair color, if youre very blonde take a dark blonde, etc - chose a tint darker than your actual eyebrow color).
Do it a day where you KNOW you’re not going out the day after, because you will have stains on your forehead - to minimize that, before dyeing, rub some vaseline on the skin around your eyebrows (dont put any on the hair though or it won’t absorb color). Use a spoolie or a small brush to apply - you really don’t need a lot, so don’t use all of the dye, just a very small amount.
Make sure to follow the recommendations on the box, like the allergy testing and stuff. They do warn you on the box not to use on eyebrows, but it’s only because they don’t want you getting product in the eyes (please be careful).
When I did that the first time, I was pre-T and got immediately gendered correctly after going out, it was so nice!
Any box dye will do, I always went for the cheapest in my color. You can also use it to dye your peach fuzz or facial hair if you have some, but I don't really recommend it as it leaves a lot of stains if you don't have enough hair to absorb it, it all goes on the skin. Also eyebrow hair get replaced pretty quick so it will fade away.